Window Board Secret Fixing

[Garden Shed Projects]

Hi can any one offer any tips for secret fixing a window board. I have one to fit at 3600mm x 350mm in my extension and am thinking gripfill or similar but wondered if there was any innovation or technique I am not aware of. The walls and reveals are already plastered.

Any ideas greatly received.

 

[Phil Pascoe]

Gun polyurethane - ensure you have weights to keep the board in place and that it can't shift from level. The stuff expands. Get rid of all dust and damp down the surfaces. No second attempts.

 

[johnnyb]

Hybrid silicone? gripfills OK but not used loads these days(I've not used it for over a decade) gun grade pu foam which is what phils saying?
Hybrid silicone is used for everything
Plumbing decorating sealing gluing but it's real sticky messy muck for sealing stuff not recommended. Normal silicone works fine to.

 

[niall Y]

One way to do this mechanically, is to rely on a fix at the back of the window board, using a bare face tenon along the length of the window board, inserted into the groove on the inside of the window sill.

The front is fastened down using Galvanised strap or angle brackets screwed to the underneath of the board, and to the wall beneath This is more convenient to do before plastering, but it is a simple enough operation to house the straps deep enough into the plaster and fill after fixing.

EDIT.
For a really neat fix, the sides of the window board can be partly recessed into the reveals, cutting the tops and bottoms of the housing with a multitool, before chiselling out the waste, and filling after the board has been installed.

 

[RobinBHM]

As Phil says gun adhesive.

But if it’s going on cell on type blocks then I would vacuum them then coat with something to seal them first.

If the windowboard is mdf it’ll hold but if it’s solid timber you need mechanical fastenings to stop cupping


https://www.screwfix.com/p/dow-inst...57l9lc75k7Xc74AQeGAaAtELEALw_wcB&gclsrc=aw.ds

 

[Chubber]

+1 for multi tool using a scrap of board thinner than the window board by the thickness of the blade if you are working off a flat plane surface?

 

[Ollie78]

Use a t slot cutter to put a few of slots in the board from the back edge to about three quarters of its width. Do a small test bit to the same depth.
Mark the positions on the substrate and install some pan head screws in line with the slots using appropriate plugs or whatever, 2 per slot, front and back.
Use the test bit to check the height of the screws and when its just right slide the board in. You want a little bit of resistance but not loads.
I am assuming a solid wood window board, I have done it on loads of Oak ones and some Utile, might need to be careful on MDF as its quite weak.
Use a bit of stixall or other hybrid polymer as well if you feel like it.

 

[Dave Moore]

CT1

 

[Garden Shed Projects]

The surface I am fixing to is made up of PIR insulation (end grain), timber covered in tyvek and then the cavity closure. I thing the PU foam adhesive sounds like the way to go. Thanks all for all the advice.

 

[Doug B]

I’ve recently removed some new skirting that had been fixed with foam & plasplode nails, it came off surprisingly easily. It wouldn’t be my choice for fixing window boards.

 

[Fergie 307]

All those in my extension, similar construction and MDF boards, were done using the solvent version of Screwfix own no more nails. Solid as a rock. Any exposed block work can be sealed first with PVA.
Method like Ollie's if they are solid wood in case they warp. I only have one original window board in the whole house. Solid pine installed in 1918, and assume held in the same way as the others with cut nails into wood noggins between the bricks. That one is distinctly bendy in both directions

 

[Fergie 307]

I’ve recently removed some new skirting that had been fixed with foam & plasplode nails, it came off surprisingly easily. It wouldn’t be my choice for fixing window boards.

Interestingly I found that skirting boards held on with solvent free no more nails can actually be peeled off as it were using a thin pallete type knife, and leave nothing behind but a slight discolouration of the plaster.

Never had one come free on its own, but relatively easy to remove if you do need to.

I put all mine on this way and have never had one come off in twenty odd years, but have had to remove a few sections for one reason or another and fully expected to have to do a bit of remedial work on the plaster, so quite a bonus.

If the wall isn't quite flat then I just screw a batten on the floor about a foot in front of the skirting and use off cuts to wedge against it while the glue dries.

 

[scooby]

I usually use expanding foam, as Phil said. Get it all the packing done before hand so its level and straight, foam it and weight it down.
Speaking of skirting, I fitted some in a house in about 2002. Went back a few years later to do an extension, which required removing some of the skirting. I used some sort of solvent fee adhesive (can't remember which) and it came off the plaster surprisingly easily (pretty mach as Fergie said). Ive always used grip fill or some other solvent type since then. Even though everyone hates the smell.

 

[Stevekane]

Many years ago I rather stupidly ordered a short length of windowboard at a timber merchant and nearly fell over when I was told the price,,I now treat any I have with great care and happily plug and patch, add strips on etc and even though they are polished they still look good to me, any new ones I make myself from any thickness board I have. My fixing is to fit under plaster if I can, I set a couple of big screws in the underside, drill matching holes in the blovkwork/bricks to take the heads and then gun in any silicon type sealant I have open into the holes and a squiggle on the board itself and drop into place. Either filler or silicon type sealant along the edges and its well stuck. I personally detest the MDF ones, and have had to fill/repair a couple of soggy ones for people.

 

[Garden Shed Projects]

The window board I have ordered is made up of 25mm MR MDF. For me if it’s painted MDF, being more stable than timber and generally makes for a better finish. I have bought it in 1 piece so don’t want to have to deal with filled screw holes.